This invention relates to an optical array and, in particular, to a one-time programmable optical array for conveying optical information.
One application for optical switches is in the optical communications field, where each xe2x80x9ccellxe2x80x9d in the array is controlled to either reflect light or not reflect light. One embodiment of such a switch comprises an array of electromechanically controlled micro-mirrors. The angle of each mirror is controlled to selectively reflect light (carrying a data stream) from an input optical fiber to another fiber. Such micro-electromechanical switches are generally referred to as MEMS switches. These devices are popular due to their flexibility but, due to the mechanical nature of their operation, they can be sensitive to vibrations and contamination.
Other types of optical switches include liquid crystals, electro-optic devices, acousto-optic devices, and thermo-optic devices.
Each of the presently known optical switches is complex, relatively expensive, and requires complex control circuitry. Such optical arrays can not only be used for dynamic switching of optical information but can also be used as a static memory, whereby stored bits are represented by whether a location on an array reflects light in a particular direction or not at all. In many applications, the flexibility of the dynamically controlled optical switches is unnecessary and adds a significant cost to the optical system.
What is needed is a simple, reliable, and inexpensive optical switch.
In one embodiment of the invention, an array of programmable zener diodes constitutes an optical switch array. Zener diodes in the array are formed such that when a sufficiently high programming current flows through the zener diode, aluminum atoms from a contact are caused to quickly migrate laterally between the anode and cathode contacts to form a conductive filament. Such diodes are frequently used as anti-fuses. Programming such zener diodes is commonly referred to as zapping. This resulting aluminum filament (or ribbon) is reflective and can act as a tiny mirror for reflecting light. Since these zener diodes may each be less than about 10 microns wide, a large number of these zener diodes may be formed on a substrate using conventional photolithographic processes.
In one embodiment of a system using such a zener diode optical array, optical fibers are arranged proximate to the array of switches, and whether a zener diode is xe2x80x9czappedxe2x80x9d or not determines whether light exiting an optical fiber is reflected back into another optical fiber.
In another use of the invention, ultraviolet light may be reflected off the optical array, and the reflection is used in a photolithography process to selectively expose photosensitive portions on another substrate. The light source may be a laser or other source. Such an inexpensive optical array may be used instead of a mask for prototyping or for other uses, such as creating biochips incorporating DNA microarrays.
Other applications of the array are described herein. Other types of one-time programmable elements besides zener diodes may also be used to create reflective metal portions on a substrate.